text: 
  let nextToDoID = 0
  // action 是指代一些抽象的行为
  // 一跳数据的 action ADD 
  export const AddToDo = ( text ) =>{
    return {
        type: 'ADD_TODO',
        id: nextToDoID++,
        text
    }
  }
  
  export const setVisibility = (filter) => {
      return {
          type: 'SET_VISIBILITY',
          filter
      }
  }
  
  export const toggleTodo = ( id ) => {
      return {
          type: 'TOGGLE_TODO',
          id
      }
  }
  export const deleteTodo = ( id ) => {
      return {
          type: 'DELETE_TODO',
          id
      }
  }